This application is based on and incorporates herein by reference Japanese Patent Applications No. 2000-11629 filed Jan. 20, 2000 and No. 2000-363044 filed Nov. 29, 2000.
The present invention relates to an engine control unit, and particularly to an engine control unit which generates frequency-multiplied signal train.
An engine control unit (ECU) is an electronic control unit for performing controls such as fuel injection control, ignition timing control, and idle speed control to operate an engine in an optimum state. Specifically, signals from various sensors for sensing engine operating states such as crank angle sensor and engine coolant temperature sensor are supplied to an the ECU to control an optimum fuel injection amount, injection timing, ignition timing, and the like.
Controls synchronized with the engine speed such as ignition control and injection control, that is, controls synchronized with a crankshaft rotation position are performed by generating a signal of ignition pulses or the like after elapse of offset (delay) time from a predetermined crankshaft position indicated by the edge of a crank signal.
It is, however, necessary to perform an arithmetic operation for converting the angle to time. There is a demand for reduction in processing load and improvement in accuracy.
It is therefore an object of the present invention to provide an engine control unit with reduced processing load and improved accuracy and, moreover, capable of properly controlling the engine even when a pulse interval in a crank signal becomes long.
According to the present invention, a crank signal is generated as a pulse train of every predetermined angle interval corresponding to rotation of a crankshaft of an engine. An edge time measuring counter receives the crank signal and measures an interval of pulses. A frequency multiplication counter generates frequency multiplication clocks of integer times by the next pulse on the basis of a pulse interval of this time. A reference counter counts the number of waves of the frequency multiplication clocks between pulses in the crank signal. When the count value of the reference counter reaches a frequency multiplication number, a guard counter forcedly stops outputting of angle clocks which are outputted in response to generation of frequency multiplication clocks in a tracking counter.